1. Field of the Invention
This invention relates to the nut and bridge nodal points called witness points, as well as frets, and finger boards and the tremolo bridge assembly as used on guitars, basses, pedal/lap steel, piano, and other instruments in the stringed family.
2. Description of the Prior Art
Guitarists want to provide a tremolo action to their playing style. Many tremolos have been devised over the past 50 years. They range in design from tremolos that functionally allow only changes in pitch downward to modern tremolos that allow pitch changes in both directions. A few books that discuss modern electric guitar and bass design, for example, are "Electric Guitar" and "Introduction to Scientific Guitar Design" by Donald Brosnac and "Constructing a Solid Body Guitar" by Roger H. Siminoff.
Many design problems exist in the tremolos over the last 15 years. The most important problem is one of staying in tune. The problem is experienced by the user as strings changing pitch during play due to string metal creep and plasticity. Also standard tuning machines have a tendency to rotate, backlash, and experience beam flex at the stem, providing a further causation of a changing string tension and thus pitch.
To date these issues have been addressed in a number of ways. The first basic method was to provide a nut system witness point that locked the string but allowed the tremolo to move freely. Tuning in this system can only be performed by microtuners or by unlocking the string at the nut, with a wrench. The second type of nut system allows the string to move freely across it. Tuning in this system would be either by standard machine tuners or tremolo microtuners.
Tremolos have had several basic designs, which include a bridge witness point that is a hard knife edge that structurally flexes to allow axial string motion, a roller under each string which provides an upward radial force allowing free axial string motion, and a fixed portion of the tremolo movable assembly so that the combined strings can move axially but have radial fixation.
String dynamics are what provides for various degrees of sustain, harmonics & tone, tuning stability, and tremolo action and reaction. The problems with both of the nut witness point systems is that they do not fully provide an environment that supports the string/neck/body unitary structural combination with the proper support to optimize each of the aforementioned attributes. A major contributor to the diminishment of each of these attributes is the stick/slip action of a standard brass and bone type nut witness point. With this traditional design a V or U shaped grove is supplied to fit the individual diameter of each string, as well as that of it's relative vertical and horizontal position. However, the nature of the brass or bone material is that the string always presses its way into the material by it's axial movement and radial pressure. This is often desired by the usual thinking, and provides not only a solid radial force but, in the negative a large axial frictional force of the stick/slip kind. This force is easily overcome by the change in string tension due to tuning machine adjustment, but NOT by the micro-movements in the axial displacement component of the string motion during vibration. The nature of this type of frictional motion is highly non-linear and stochastic in nature. In addition, the nature of this type of force in combination with tuning peg problematic movement, versus intentional tuning adjustments, and knife edged and/or hook return spring based tremolo bridges, constitutes a serious departure from the structural support requirements of the ideal string dynamics as discussed herein.
Typical tremolo designs all have a large disadvantage in that the pitches of the individual strings alter significantly from the inter string pitch ratios of open string tuning. Very quickly the strings each take a different pitch trajectory from the ideal. A secondary result is the lower pitch strings reach slackness well before the higher pitch strings. In addition the pitch trajectories follow an uncontrolled path where each string has its unique and un-orchestrated pitch trajectory. Therefore even the best musician cannot control their music in a fully chromatic or even linear way. This problem precludes a fundamentally basic need in musicology of retaining chromatic order. The ability to produce inter string (note) and chromatically correct music during pitch changes is something almost any synthesizer keyboard can provide.
Secondly tremolo design has been nearly exclusively based upon variations in the knife edge pivot point and roller or edge or rotational witness point type tremolo bridge assemblies. As discussed in the previous section these bridge witness point designs have disadvantages in their approach to string support and produce an adverse effect on string dynamics.
Thirdly in addition to these disadvantages, there exists those intrinsic to knife edge and post pivot designs and hook spring return support blocks. The typical knife edge and post pivot design provides the tremolo with a cost effective way to locate the tremolo axially as well as horizontally and vertically. Usually one post has a semi-circular groove on the tremolo body while the other has a straight edge, the later to allow for location without misalignment. The tremolo body is forced into the post groove by the opposing tensions of the six strings and the two or three hook tension springs. Therefore the static and dynamic axial and radial forces of the six strings are opposed by the two slender posts and the tremolo body hook springs. The knife edge and post groove interface as well as the hook tension springs provide a series of extra resonances, energy storage mechanisms, and highly non-linear forces. Moreover as the tremolo is used and the relative angle of the tremolo body is changed so also the attack face of the knife edge and post groove interface changes, adding further to the stick/slip friction. All these actions take away from the optimum string support and thus diminish the string dynamics comprised of the sustain, harmonics and tone, tuning stability, and tremolo action and reaction.
It could be argued that these non-linear effects add to the "sound"; they may add a type of character to the sound but only detract from user control and the rest of the string dynamics.
Applicant's therefore feel the value of a complete solution to these problems lies in the user's experience of longer sustain, greater tone, more stable tone and phase decay, better feel, stable tuning, improved intonation accuracy, smoother tremolo action/reaction, and force feedback.
Appliant's shall first examine the notable prior art of guitar nut witness points in as regards to the invention, described herein, of String Bearings. The range of interesting prior art includes patents from as early as Faas U.S. Pat. No. 118,353; Hafer U.S. Pat. No. 550,268; and Eurich U.S. Pat. No. 3,695,137; to the contemporary U.S. Pat. No. 4,171,661 Rose; U.S. Pat. No. 4,475,432 Stroh; to most recently U.S. Pat. No. 4,517,874 Fender. In applicant's opinion the landmark patent of this series is that of Rose U.S. Pat. No. 4,171,661. Rose developed a good knife edge/post pivot based tremolo bridge and provided locking mechanism on both ends of the scale length of the strings; the nut and bridge witness points. This was acclaimed by Rose and the industry at the time as the way to insure maintenance of the tuning of the strings while under the strain of the tremolo operation. Many licences of the Rose system continue today producing variations of the lock nut or knife edge bridge. The main theoretical advantage of locking the strings at the Nut Witness point is the maintenance of proper tuning. However this is largely abated by the the need for bridge mounted tuners, lock nut wrenches, and the warped or deformed strings that result from their use. These disadvantages are mechanical, however the dynamic disadvantages also include less tone, instable tone and phase decay, and less smooth tremolo action/reaction, and force feedback for the user. Nevertheless at the time of the Rose patent only the mechanical disadvantages where evident and prompted Edwards U.S. Pat. No. 4,579,033 to develop and patent the Finger Operated Lock Nut. This design obviated the need for wrenches to loosen and re-tighten the clamping action on the strings. The mechanical disadvantages remain albeit less so. With this design the user must still lift the nut's locking handles and then tune/re-tune and re-tighten the handles before continuing. However this design has done nothing to improve string dynamics. It's disadvantages include less tone, instable tone and phase decay, and less smooth tremolo action/reaction, and lower force feedback. Also it is apparent from the use of the locking nut that once the instrument has been tuned that the very clamping action of the lock nut may rechange the tuning parameter once again away from the tuning where the user had previously adjusted it.
Applicant's strong opinion, and the basis for part of the Sting Bearing invention, is that in order to optimize the string dynamics as previously discussed one must allow the string to move axially over the Witness Point with only radial force present. A highly linear and high stiffness structure must provide near zero axial force due to resistance or friction. This must occur for the micro-displacement movements caused by the combinatorial motion of the string and guitar neck/body movements. These motions are on the order of acoustic and flexural displacement axial motions present in a vibrating structure such as a guitar or other stringed instrument.
Applicant's should further point out that standard bone or brass type nuts with fixed cut string groove, require adequate down pressure of the strings into the nut grooves. These grooves are intentionally cut to provide very high grabbing friction from the sides of the nut's grooves to the strings. This friction can be overcome by tuning adjustments. These structures therefore impose a large axial friction force on the strings due to the micro-displacement movements of the strings during play, thus producing an additional undesirable and adverse affect on the string dynamics. Additionally such typical nuts provide low radial stiffness whose characteristics are not linear. Moreover, when a tremolo type bridge is used the normal axial forces imposed by the tremolo action on the strings cause a stick-slip friction response by the V groove and nut interface. This type of force dynamic has an additional adverse effect on the string dynamics.
With these issues in mind it is applicant's opinion that the second landmark patent, in regards to prior art nut witness point technologies, lies in Wilkinson U.S. Pat. No. 4,709,612. Wilkinson also cites U.S. Pat. No. 2,191,776 Schrieber and U.S. Pat. No. 2,905,402 Hoyer. The Nut for Stringed Instruments amounts to a block with individual rollers supporting each string and guidance shapes such as a V shape to guide the entrance and exit of each string in their path to the tuners (this function is normally performed by a string tree guide). It should also be noted that Witness Point technology for the Bridge end can be found in various roller forms such as Storey U.S. Pat. Nos. 4,457,201 and 4,487,100. These rollers however are in a pulley form with a true bearing while Wilkinson's are of the wide cylindrical type riding on their circumferential area. The problems with the Roller Nut are manifold. Practice has shown that the strings do not actually cause the rollers to rotate because of the opposing friction force generated between the rough body's interior and the small diameter roller. In fact the string slides and deforms while crossing the small diameter rollers. The resulting string deformation is plastic, not elastic, and causes many problems in the string dynamics, as previously discussed. Even true pulley rollers, as in Storey's design, have this mechanical behavior in response to the aforementioned micro-displacement movements present in real vibrating systems. It should be pointed out that the Roller Nut does provide the benefit of Tuning adjustments that can be performed without the aforementioned drawback of wrench operated or lever operated Lock Nut designs. These adjustments however comprise relatively gross axial motions in comparison to the aforementioned micro-displacement movements present during string vibration. A final disadvantage of the Wilkinson Roller Nut is that the friction due to the aforementioned micro-displacement movements is exacerbated by the string's rubbing on the sides of the V shape entrance and exit areas.
Applicant's have not discovered any prior art that covers the issues of vertically, horizontally, axial, or any other combination thereof, adjustable nut witness points.
These nut systems, as well as standard bone or brass fixed cut groove style nuts often require a string tree guide for several of the strings. String trees help to maintain an adequate down pressure of those strings into the nut grooves. These structures also impose a friction force, or even plastic deformation force due to the micro-displacement movements of the strings, thus producing additional undesirable results.
The value of solving the problem of the nut witness point lies in improving the string dynamics which in turn allows the user to experience longer sustain, greater tone, more stable tone and phase decay, better feel, stable tuning, improved intonation accuracy, smoother tremolo action/reaction, and force feedback. Operational and mechanical improvements should include: no nut wrench or handle adjustments required, strings do not become plastically deformed (kinked), tuning adjustments are single step only, intonation adjustments are easier, no string tree guides should be required, and strings should not cut themselves deeper into the nut grooves with time. These improvements reduce maintenance cost as well.
The requirements for a novel solution to these problems should provide a basis that allow the dynamics of the strings and instrument structure combination to truly move freely in the axial direction while simultaneously transmitting the vibratory forces of the strings into the instrument without loss or distortion in the radial direction.
Applicant's shall demonstrate that the string bearing invention described herein meets or exceeds these requirements.
Applicant's shall secondly examine the notable prior art in as regards as to Tremolo Bridges. From the early patents such as Faas U.S. Pat. No. 118,353; Van Dusen U.S. Pat. No. 462, 519; Weber U.S. Pat. No. 509,414 and Farigenele U.S. Pat. No. 2,214,957 to the early Fender patent U.S. Pat. No. 2,741,146; and followed by Burns U.S. Pat. No. 3,196,729. Many patents on fixed and tremolo bridges exist.
However the landmark patent in applicant's opinion is that of Rose U.S. Pat. No. 4,171,661. Rose developed a good knife edge/post pivot based tremolo bridge and provided locking mechanism on both ends of the scale length of the strings; the nut and bridge end. Licensing of the Rose system as enforced by his patent continues today. The main issue that appears to be both unique as well as enforceable is the knife edge and post pivot claim.
Some of the most notable tremolo patents are: Storey U.S. Pat. No. 4,457,201 & U.S. Pat. No. 4,487,100 and Wilkinson U.S. Pat. No. 4,709,612. Some tremolo and fixed bridge patents are:
______________________________________ U.S. patents 118353 3563126 4464970 4843941 D269440 462519 3695137 4475432 4856404 D290017 509414 4171661 4487100 4867031 D302563 550268 4206679 4538498 4913024 RE32863 2191776 4230014 4574678 4928564 2214957 4334454 4579033 D244051 2741146 4430919 4677891 D260271 2905402 4464970 4709612 D268272 3196729 4517874 4724737 D269438 3453920 4457201 4811646 D269439 Foreign Patents 620858 3996 72716 ______________________________________
The Rose patent is a landmark primarily because of the knife edge and post pivot design. The Storey patents are interesting because of the micro-tuner and height adjustments as well as mono-cam style rotation of the bridge end string terminations. Important is the "autolatch" device which allows the user to lock the tremolo into neutral center position by use of the tremolo bar rotation. The Wilkinson patent shows an elegant string termination method. Practically however the pivot design is a variation on the Rose patent.
These patents have no bearing on the invention herein described.
Additional prior art of significance is from the Steinburger company. They have developed and are now selling a tremolo with a form of pitch correction. No patents appear at the time of this writing to be issued. The units sold have been marked with the phrase "Patent Pending" and are called the `TransTrem`. The tremolo has been designed to provide for locking the device at specifically calibrated positions in order to allow the user to put the tuning up or down specific steps in pitch. This function is called transposition and has been performed using a typical Capo which is applied on the finger board near the top (nut end) frets. After examination of the production tremolo device applicant's have observed that it has a rotatable assembly with six saddles, one per string. The strings terminate in the saddle whose relative circumferential adjustment allows that each string will have a unique fixed effective radii from the assemblies effective center of rotation. Applicant's have, in applicants work with the invention described herein, proved that such a structure can only provide an effective inter string pitch correction if the set of effective radii that are produced during the assembly's rotation are exact. Applicant's have determined that the Steinburger design could only provide inter string pitch correction within a narrow range or rotation. It is therefore inadequate and inexact for this first task. Furthermore the Steinburger has no facility to provide chromatically correct, or any other, pitch trajectory control. Its ability to provide a transpositional function is derived from calibrated steps provided for the user to leave the tremolo in a particular position to achieve say a step or half-step down. This function is NOT an intrinsic aspect of their design but is no doubt the result of a trial and error effort which resulted in the development of tremolo angle position indentations that provide only specific settings. The use of theoretically constant radii CANNOT provide any continuously chromatic functioning. Furthermore the design that applicant's have inspected is not capable of accurate inter string pitch correction and may not provide true pitch coherence as well.
Most of these tremolo designs have several major drawbacks in their design from a string dynamic, as well as a guitar neck & body dynamics, point of view. Primarily they are the vibratory and acoustic dynamic characteristics of the knife edge and post pivot and those of the hook return springs. Secondly their use of rotating, flexing, or V groove Bridge Witness points is also a large drawback.
The drawbacks of the knife edge and post pivot design lay in three areas. The first is in the rotational micro-angular changes in the interface between the groove on the tremolo support base plate and the post knife edge type head. This changing interface is highly non-linear and contributes mechanical noise to the subtle displacements due to the string/instrument dynamics. Secondly, the interface itself between the knife edge post head and the base plate screw along with the contribution of the changing interface attack surface, is one whose mechanical acoustic wave signal impedance characteristics are dubious. The impinging stress wave due to the normal string dynamic cannot easily pass through this pivot structure without large distortion and reflection. Thirdly, the post itself is a resonant structure of fairly high resonant frequency which should on first examination be in the upper frequency range of musically useful interest. On further examination one can see a highly unusual acoustic/mechanical impedance mismatch between the various guitar components such as the neck, body, even the tuning pegs and the two small pivot posts on the typical tremolo. The various guitar components such as the neck, body, and the tuning pegs (1 per string) have a much higher stiffness and certainly more stable acoustic/mechanical impedances than do the two small posts that must carry the entire reactive force component into the body of the guitar in both radial as well as axial directions.
The drawbacks of using hook springs to provide return action in opposition to the strain of the strings in these tremolo designs lies in a similar way to the drawbacks inherent in the knife edge post, namely they are insuffcient nonlinear mechanical elements with regards to stress wave mechanical signal impedance. Unlike posts, hook type return springs have fundamental resonant frequencies within the frequency bands of interest. They contribute both resonant and anti-resonant peaks to the response spectra of the structure. This effect is most often to the detriment of the dynamics, and playability, of the instrument.
The drawbacks of rotating, flexing, V groove, and pulley Bridge Witness points lies in several areas. For rotating cam like witness points as found on many tremolo bridges such as Storey and Wilkinson, they lack a true witness point. Namely the string flexes around the surface of the cam and does not actually have a radial witness point per se. Only friction and the final anchor point provide a radial reactive force component. In addition most designs actually move the witness point axially while rotating. For flexing type witness points the drawbacks include that the witness point moves axially as well as the string must drag the witness point structure along with itself by only the friction between them. For typical rigid V groove witness point bridges the strings have a large friction force axially as well as a stick-slip friction response action. Lastly for pulley type witness points, they provide low axial friction but add an undesirable dynamic due to the mechanical clearance of the elements. Moreover usually this pulley type witness point has been made to move its effective axial position with the tremolo rotation causing the overall string length to change with operation. All these aforementioned actions provide undesirable results by combining both string tension and length based pitch changes simultaneously, and add a frictional element that is highly non-linear and damping on the vibratory string dynamics. All these actions are clearly undesirable from the point of view of string dynamics, intonation, tonality, and playability.
The final major drawback of all these prior art tremolo designs is they lack the ability to maintain a relative and accurate tune between the six strings. This is true because when all the strings have a relatively fixed relation among them the high strings will provide a different pitch change factor than the lower strings for an equal change in string length. This is because the typical tremolo designs such as Storey and Rose change the displacement of all the six strings equally.
Such equal displacement change CANNOT provide for constant inter string tuning nor for any type of pitch trajectory control.
Mechanically, the ideal for a witness point and tremolo bridge is:
First to maintain a constant string length by not moving the positions of the nut or bridge witness points.
Secondly, provide for the strings to be elastically strained to provide the pitch change.
Third, the strings must remain in relative open tuning pitch ratios to one another while the overall tremolo pitch change occurs during tremolo operation.
Fourth, the trajectories of the pitches of the strings must be controlled to provide continuous and accurate, chromatically correct music.
Fifth, the ideal in an acoustic wave sense for a witness point and tremolo bridge is to allow the acoustic mechanical stress waves to pass through the tremolo structure without gross mechanical impedance changes and without resonant structures with resonant frequencies either in the band of interest or with transient responses much less than those of the neck and strings and the other major mechanical guitar components.
No prior art patented or not patented, known to these writers provides these five criteria in total or in majority.